The present invention concerns a device, an arrangement and a method for opening or separating two closely joined sheets of flexible material, e.g. sheets or folded pieces of film or paper, by applying vacuum on opposite external sides of these joined layers. The device includes at least one pail of mutually opposite leaves that are pivotably connected along an edge at a lower part of the leaves, and where at least one leaf is provided with an bend at a centre area, the bend directing an upper part of the leaf outward and away from the opposite leaf so that at least one of the upper leaf parts is oriented away from the opposite upper leaf part the leaves each being provided with an aperture adapted as connection for a vacuum source.
Typically, we are speaking of opening different packing wrappers or large bass or envelopes to be opened for receiving inserts, e.g. sundry advertisement prints, and which are to be handled with great safety and rather large capacity, e.g. 5000 to 25,000 pieces per hour.
It is wellknown to open flat wrapper items by means of suction cups which are sucked fast on opposite sides and then moved from each other, but since it is nearly always very difficult to pull two closely joined sheets from each other, this method has not appeared to be sufficiently sure for reliable operation with high capacity.
By the present invention, the joined sheets are guided into a wedge space with folding walls which in the folded state squeezes an intermediate area of the sleets between perforated, local wail parts for applying subpressure from outside, the perforations being connected with grooves extending in the outward direction at the inner sides of the walls, i.e. outward towards the external opening of the said wedge space, as at least one of these inner wall sides outside the said local wall parts continues in an outward bending course towards the outer opening for forming an outer wedge space in the folded state of the walls.
The invention is peculiar in that the connection to the vacuum source is arranged via an opening at a position below the bend, and that this opening is connected with one or more grooves extending in the surface of the side walls from the position under the bend, past the bend and to a position on the upper, outward bending leaf part.
Furthermore, the invention concerns an arrangement including a number of devices according to the invention and peculiar in that the devices are radially mounted in star configuration on a rotary wheel, so that the opening of each device faces away from the centre of revolution of the wheel.
Finally, the invention concerns a method being peculiar in that
the joined sheets are inserted between two leaves, of which one leaf is partly bent outwards and away from the opposite leaf;
the leaves are moved towards each other by turning about a common connection axis,
vacuum is established through a number of perforations provided in the leaf surfaces and facing the joined sheets, whereby the outer layers of the sheets is sucked onto each leaf surface;
the suction against the leaf surfaces propagates successively up along the sheets; and
the two leaves are tilted away from each other with the sheets sucked upon each their leaf.
Quite a few tests with xe2x80x98opening flapsxe2x80x99 have been unsuccessful, but with the above, rather simple measures a surprisingly efficient and reliable function of the devices has been noted, also by high capacity and at least in the case of handling items which are not completely airtight. The items are opened by a successive mutual xe2x80x9cpeeling offxe2x80x9d, which appears to be considerably more reliable that attempts on a plane parallel pulling. The effect may somehow be difficult to explain, but it has been demonstrated that it is attainable.
It is to be mentioned that the invention provides for a further and attractive application, namely opening not only double sheets but also folded multilayer products joined at the back, such as newspapers. It is common practice that diverse inserts, e.g. in the form of regional or special supplements, are to be laid into folded newspapers delivered from a rotary press, and that it is prior art to perform a required opening of the folded newspapers by means diverse mechanical gripping and opening means. These, however, are to operate so quickly that operational problems may arise, and the present invention is interesting as a possible alternative or supplement to this technique.
The invention may particularly be considered when it is provided that the mentioned opening by vacuum occurs close to the side edge of the folded item which is constituted by the back edge of the unfolded item as the transfer of the opening action to the other sheets in the item then will occur immediately through the item back edge. If at one side edge of the folded item there is formed a reliable initial opening of the item at first, it may, if needed, be secured with other means that his opening propagates rapidly along the rest of the folded item.
In connection with the present invention xe2x80x9cupperxe2x80x9d and xe2x80x9clowerxe2x80x9d are not to be understood as concerning vertical orientation, but are only indicating an orientation farther from or closer to the pivotable connection between the walls.